Encoder and control system

ABSTRACT

A control system includes an encoder and a control device that controls a target object by using information transmitted from the encoder by serial communication. The encoder includes a position information generating unit that generates position information made of a predetermined amount of data and including absolute position data of an object to be detected; a configuration information generating unit that generates configuration information representing a ratio of the absolute position data in the amount of data during serial communication; and a transmission unit that transmits, to the control device, the position information and the configuration information as a series of serial data. The control device includes a reception unit that receives the position information and the configuration information transmitted from the encoder; and a control unit that processes the position information received by the reception unit on the basis of the configuration information received by the reception unit.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an encoder and a control system.

2. Description of the Related Art

In a control system that includes an encoder that performs serialcommunication, the encoder receives a signal from a control devicerequesting position information and communicates the positioninformation generated at a certain timing on serial data. Here, anamount of data of the position information held by the encoder, that is,an amount of multi-rotation data of an object to be detected and anamount of the position data within a single rotation, varies dependingon the encoder. In particular, in a battery-less encoder that backs upthe multi-rotation data representing a number of rotations of the objectto be detected in the encoder alone, the amount of the multi-rotationdata may vary depending on the battery-less method and the size of theencoder.

Thus, a serial interface method is reported, in which the type of datatransfer format of the encoder being used can be automaticallydetermined and processed by a CNC (a computer numerical controldevice)(JP 5-113809 A, for example).

However, in an encoder that performs serial communication, when theamount of the multi-rotation data and the amount of the position datawithin a single rotation are determined in a specific format, there is aproblem that the amount of data may not be satisfied depending on theencoder, and the correct position data cannot be obtained.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an encoder and acontrol system capable of performing communication of positioninformation in an optimal format for the encoder.

A control system according to an example of the present disclosureincludes an encoder and a control device configured to control a targetobject by using information transmitted from the encoder by serialcommunication. The encoder includes a position information generatingunit configured to generate position information made of a predeterminedamount of data and including absolute position data of an object to bedetected, a configuration information generating unit configured togenerate configuration information representing a ratio of the absoluteposition data in the amount of data during serial communication, and atransmission unit configured to transmit, to the control device, theposition information and the configuration information as a series ofserial data. The control device includes a reception unit configured toreceive the position information and the configuration informationtransmitted from the encoder and a control unit configured to processthe position information received by the reception unit on the basis ofthe configuration information received by the reception unit.

According to the encoder and the control system according to the exampleof the present disclosure, it is possible to perform communication ofposition data in an optimal format for the encoder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of a control system according toExample 1.

FIG. 2A is a diagram illustrating a configuration of positioninformation of an encoder in the control system according to Example 1.

FIG. 2B is a diagram illustrating an example of position information ofan encoder in the control system according to Example 1.

FIG. 2C is a diagram illustrating another example of positioninformation of an encoder in the control system according to Example 1.

FIG. 2D is a diagram illustrating yet another example of positioninformation of an encoder in the control system according to Example 1.

FIG. 3 is a diagram illustrating an example of position information ofvarious types of encoders when a configuration of position informationis fixed in a specific format.

FIG. 4 is a timing chart of a position information request signaltransmitted by a control device and of a response signal transmitted byan encoder in the control system according to Example 1.

FIG. 5 is a configuration diagram of a control system according toExample 2.

FIG. 6 is a timing chart of a position information request signal or aconfiguration information request signal transmitted by a control deviceand of a response signal transmitted by an encoder in the control systemaccording to Example 2.

FIG. 7 is a configuration diagram of a control system according toExample 3.

FIG. 8 is a diagram illustrating an example in which configurationinformation transmitted from an encoder changes in the control systemaccording to Example 1.

FIG. 9A is a diagram illustrating a state in which a control devicestores configuration information initially transmitted from an encoderin the control system according to Example 3.

FIG. 9B is a diagram illustrating an example in which, in the controlsystem according to Example 3, after a storing of configurationinformation initially transmitted from an encoder, the configurationinformation transmitted a next time has changed.

DETAILED DESCRIPTION

Hereinafter, an encoder and a control system according to the presentinvention are described with reference to the drawings. However, thetechnical scope of the invention is not limited to these embodiments andincludes the invention described in the claims and elements equivalentthereto.

First, a control system according to Example 1 is described. Aconfiguration diagram of the control system according to Example 1 isillustrated in FIG. 1. A control system 101 according to Example 1includes an encoder 1; and a control device 2 that controls a targetobject by using information transmitted by serial communication from theencoder 1.

The encoder 1 included in the control system 101 according to Example 1includes a position information generating unit 11, a configurationinformation generating unit 12, a transmission unit 13, a sensor unit14, and an analog-to-digital (A/D) converter 15. The encoder 1 isprovided in the vicinity of a motor 10 that is an object to be detectedand detects a position and a movement speed of a rotation shaft (notillustrated) of the motor 10.

The sensor unit 14 detects the movement of the rotation shaft of themotor 10 that is the object to be detected and outputs an analog signalcorresponding to a movement distance of the rotation shaft. The A/Dconverter 15 performs A/D conversion on the analog signal output fromthe sensor unit 14 and outputs a digital signal.

The encoder 1 receives, from the control device 2, a positioninformation request signal requesting the position information of theobject to be detected.

The position information generating unit 11 generates positioninformation that is made of a predetermined amount of data and thatincludes absolute position data of the object to be detected (the motor10, for example). When the encoder 1 is a linear encoder, the positioninformation is configured by the absolute position data. On the otherhand, when the encoder 1 is a rotary encoder, the position informationis configured by multi-rotation data and the absolute position data(position data within a single rotation). Here, the term “amount ofdata” refers to a total number of the number of bits representing theamount of the multi-rotation data and the number of bits representingthe amount of the absolute position data, that is, the total number ofbits. The amount of data is predetermined as a format of the serialcommunication between the encoder 1 and the control device 2.

FIG. 2A illustrates a configuration of the position information of theencoder in the control system according to Example 1. FIG. 2Aillustrates an example in which the predetermined amount of data of theposition information is 28 bits. The position information is configuredby the multi-rotation data of X bits and the absolute position data of Ybits. In the example illustrated in FIG. 2A, the sum of X and Y is 28.

The configuration information generating unit 12 generates configurationinformation representing a ratio of the absolute position data in theamount of data during the serial communication. Here, the ratio isexpressed by the distribution of the amount of the multi-rotation dataand the amount of the absolute position data; or a position of aboundary between the different types of data; and the like. Theconfiguration information includes information about the amount of theabsolute position data. In the example illustrated in FIG. 2A, theconfiguration information can be expressed by the amount of themulti-rotation data (X bits), by the amount of the absolute positiondata (Y bits), or by both of the amounts of data in the predeterminedamount of data (28 bits). For example, the configuration information canbe represented by (X=m), by (Y=n), or by (X=m, Y=n) (where m and n arepositive integers). In this case, the sum of m and n is the amount ofdata (m +n) of the position information. Since the amount of data (m+n)is known, when the amount (X=m) of the multi-rotation data is receivedas the configuration information, it is possible to calculate the amountof the absolute position data (Y=m+n−X=n), and when the amount (Y=n) ofthe absolute position data is received, it is possible to calculate theamount of the multi-rotation data (X=m+n−Y=m).

In this manner, the position information generating unit 11 generatesthe position information including the absolute position data and themulti-rotation data of the object to be detected, and the configurationinformation generating unit 12 generates the configuration informationrepresenting the distribution of the absolute position data and themulti-rotation data in the amount of data during the serialcommunication.

The transmission unit 13 of the encoder 1 transmits, to the controldevice 2, the position information corresponding to the configurationinformation, together with the configuration information. The positioninformation generating unit 11 and the configuration informationgenerating unit 12 of the encoder 1 can be realized by hardware, such asa circuit implementing the functions thereof, or can be realized by acomputing device, such as a CPU, using software implementing functionsequivalent thereto.

The control device 2 includes a reception unit 21 and a control unit 22.

The reception unit 21 receives the position information and theconfiguration information transmitted from the encoder 1. In the exampleillustrated in FIG. 1, the reception unit 21 of the control device 2receives the position information and the configuration informationtransmitted by the transmission unit 13 of the encoder 1.

The control unit 22 processes the position information received by thereception unit 21 on the basis of the configuration information receivedby the reception unit 21.

Here, in order to explain a specific example of the configurationinformation, FIG. 3 illustrates an example of the position informationin various encoders in a case in which the configuration of the positioninformation is fixed in a specific format. As illustrated in FIG. 3, aformat is given as an example of the serial communication in which theamount of the multi-rotation data is specified as 12 bits and the amountof the absolute position data is specified as 16 bits, of the positioninformation of the predetermined amount of data (28 bits).

When each of the amounts of data is specified in the format of thecommunication, the encoder needs to fill the number of bits describedabove. However, in a battery-less encoder or the like, the amount of themulti-rotation data, that can be output, varies depending on thebattery-less method and on the size of the encoder, and it may not bepossible to fill the number of bits in the format.

As with an encoder A illustrated in FIG. 3, in a battery-less encoder inwhich the amount of the multi-rotation data is only 11 bits, theabove-described format cannot be filled, and missing bits arise. If thisis not addressed, a problem arises when the encoder has rotated by 12bits (4096) or more. Therefore, processing is required to mask the mostsignificant bit of the amount of the multi-rotation data, on thereception side of the position information. However, in a case where theamount of the multi-rotation data held by the encoder cannot beautomatically determined, some parameter settings need to be performedmanually.

In contrast, in the encoder 1 according to Example 1, of the positioninformation in the format of the serial communication, the configurationinformation, which is the information by which the amounts of themulti-rotational data and the absolute position data held by the encoder1 are ascertained, being transmitted using the serial communication fromthe encoder to the control device 2. As a result, it is possible toperform control using an optimum format for the encoder 1.

In other words, according to the encoder according to Example 1, in thecase of the encoder A, by transmitting to the control device that, ofthe 28 bits of the position information, the amount of themulti-rotation data is 11 bits or the amount of the absolute positiondata is 17 bits; or transmitting both of these, the control device candetermine the configuration of the position information transmitted bythe encoder, and optimal control can be achieved without performingmanual parameter setting. FIG. 2B illustrates an example of the positioninformation of the encoder in the control system according to Example 1.According to the encoder according to Example 1, the configurationinformation generating unit 12 generates the configuration information(X=11, Y=17) in which the amount of the multi-rotation data of theencoder A is 11 bits and the amount of the absolute position data is 17bits. In this case, a least significant bit d0 of the absolute positiondata is missing, and thus, for example, a value of 0 may be assigned.Since d0 is the least significant bit, it does not significantly affectthe accuracy of the data.

In addition, as with an encoder B in FIG. 3, there may be a case inwhich, for the improvement in resolution, more of the absolute positiondata is output than the multi-rotation data. However, in a case wherethe amount of the absolute position data is determined to be 16 bits bythe format of the serial communication, 5 bits of the lower-levelabsolute position data cannot be transmitted, and a problem arises inwhich the superiority of the high-resolution encoder is lost.

FIG. 2C illustrates another example of the configuration of the positioninformation of the encoder in the encoder according to Example 1. Asillustrated in FIG. 2C, in the encoder according to Example 1, in thecase of the encoder B, it is possible to make use of the high resolutionof the encoder B because the configuration information (X=7, Y=21) inwhich, of the 28 bits of the amount of data, the amount of themulti-rotation data is 7 bits and the amount of the absolute data is 21bits, can be specified on the encoder side.

In addition, as with an encoder C in FIG. 3, in an encoder (primarily alinear encoder) that does not require the multi-rotation data, themulti-rotation data is not present, and it is thus necessary to transmitall the data as the absolute position data. However, there has been aproblem in that optimum data cannot be transmitted when the presence ofthe multi-rotation data is specified as the configuration of theposition information in the format of the serial communication.

FIG. 2D illustrates yet another example of the configuration of theposition information of the encoder in the encoder according toExample 1. As illustrated in FIG. 2D, in the encoder according toExample 1, in the case of the encoder C, the transmission of the optimumdata can be performed because the configuration information (X=0, Y=28),in which, of the 28 bits of the amount of data, the amount of themulti-rotation data is 0 bits and the amount of the absolute positiondata is 28 bits, can be specified on the encoder side.

In the above description, as an example of the configurationinformation, the information is given indicating the distribution inwhich the amount of the multi-rotation data is 12 bits and the amount ofthe absolute position data is 16 bits, of the amount of data of thepredetermined amount of data (28 bits) (e.g. X=12, Y=16). However, theconfiguration information is not limited to such an example, and theconfiguration information may include information indicating a boundarybetween the absolute position data and the multi-rotation data duringthe serial communication. Specifically, the configuration informationincludes information representing the position of the least significantbit (LSB) of the multi-rotation data or of the absolute position data;the position of the most significant bit (MSB) of the multi-rotationdata or of the absolute position data; or both the position of the leastsignificant bit (LSB) and the position of the most significant bit(MSB), the positions being adjacent to the boundary between themulti-rotation data and the absolute position data in the positioninformation. For example, in the case of the encoder A in FIG. 2B, thismay be information indicating that the boundary between themulti-rotation data and the absolute position data is between an 11thbit that is the least significant bit of the multi-rotation data and a12th bit that is the most significant bit of the absolute position data,as indicated by an arrow.

Then, the serial communication between the encoder 1 and the controldevice 2 is described. The control device 2 transmits the signal forrequesting the position information (the position information requestsignal) to the encoder 1 at a predetermined cycle. The encoder 1transmits the position information and the configuration information asserial data to the control device 2 each time the encoder 1 receives therequest signal from the control device 2. The configuration informationpreferably includes the information about the amount of the absoluteposition data or of the multi-rotation data. FIG. 4 is a timing chart ofthe position information request signal transmitted by the controldevice and of a response signal transmitted by the encoder in thecontrol system according to Example 1. For example, a time at which theencoder 1 receives the position information request signal is referredto as times r1, r2, and r3 of a trailing edge of a pulse of the positioninformation request signal.

The position information generating unit 11 generates the positioninformation after a predetermined period of time from receiving theposition information request signal. In the example illustrated in FIG.1, the position information generating unit 11 generates the positioninformation of the object to be detected on the basis of the digitalsignal output from the A/D converter 15. The position informationincludes the multi-rotation data of the X bits and the absolute positiondata of the Y bits.

The configuration information generating unit 12 generates theconfiguration information (X=m, Y=n) representing the amount of themulti-rotation data (X=m), the amount of the absolute position data(Y=n), or both. The configuration information preferably includes theinformation about the amount of the absolute position data. However, ina case where the amount of data (m+n) is already known, the amount (Y=n)of the absolute position data can be calculated from the amount (X=m) ofthe multi-rotation data.

The transmission unit 13 transmits the position information and theconfiguration information as a series of serial data to the controldevice 2. In FIG. 4, for example, when the encoder 1 receives a firstposition information request signal at the time r1, the transmissionunit 13 transmits the position information and the configurationinformation as a series of serial data to the control device 2 at a timet1 after the predetermined period of time. Similarly, when the encoder 1receives a second position information request signal at the time r2,the transmission unit 13 transmits the position information and theconfiguration information as a series of serial data to the controldevice 2 at a time t2 after the predetermined period of time. Similarly,when the encoder 1 receives a third position information request signalat the time r3, the transmission unit 13 transmits the positioninformation and the configuration information to the control device 2 asa series of serial data at a time t3 after the predetermined period oftime.

As described above, by transmitting both the position information andthe configuration information each time the position information requestsignal is received, the encoder 1 can transmit the correct positioninformation even in a case where the configuration information ischanged. Examples of cases in which the configuration information ischanged include a case in which the configuration of the positioninformation is changed in accordance with the size of the positioninformation, a case in which the encoder is changed, and the like.

According to the control system according to Example 1, by transmitting,to the control device, the configuration information representing thedistribution of the amount of the multi-rotation data and the amount ofabsolute position data in the position data of the serial data from theencoder, the communication of the position data in an optimal format forthe encoder is possible.

Then, a control system according to Example 2 is described. FIG. 5illustrates a configuration diagram of the control system according toExample 2. A control system 102 according to Example 2 is different fromthe control system 101 according to Example 1 in that the transmissionunit 13 sends the position information and the configuration informationto a control device 20 as a series of serial data or as separate serialdata, in that the control system 2 further includes a storage unit 23that stores the configuration information received by the reception unit21, and in that the control unit 22 processes the position informationreceived by the reception unit 21 on the basis of the configurationinformation stored in the storage unit 23. Since the rest of theconfiguration of the control system 102 according to Example 2 issimilar to that of the control system 101 according to Example 1, adetailed description thereof is omitted.

The transmission unit 13 of the encoder 1 transmits, to the controldevice 20, the position information corresponding to the configurationinformation. The configuration information preferably includes theinformation about the amount of the absolute position data.

The position information generating unit 11 generates the positioninformation including the absolute position data and the multi-rotationdata of the object to be detected. The configuration informationgenerating unit 12 generates the configuration information representingthe distribution of the absolute position data and the multi-rotationdata in the amount of data during the serial communication. Theconfiguration information preferably includes the information about theamount of the absolute position data or of the multi-rotation data.

The transmission unit 13 transmits, to the control device 20, theposition information corresponding to the configuration information.

The reception unit 21 of the control device 20 receives the positioninformation and the configuration information transmitted from theencoder. The storage unit 23 of the control device 20 stores theconfiguration information received by the reception unit 21. The controlunit 22 of the control device 20 processes the position informationreceived by the reception unit 21, on the basis of the configurationinformation stored in the storage unit 23. By storing the configurationinformation transmitted from the encoder 1 in the storage unit 23 on thecontrol device 20 side, the encoder 1 does not need to constantlytransmit the configuration information along with the positioninformation.

Then, the position information and the configuration informationtransmitted and received in the control system according to Example 2 isdescribed. FIG. 6 illustrates a timing chart of the position informationrequest signal or a configuration information request signal transmittedby the control device and of the response signal transmitted by theencoder in the control system according to Example 2.

For example, the time at which the control device 20 transmits theposition information request signal is referred to as the times r1, r2,and r3 of the trailing edge of the pulse of the position informationrequest signal.

The position information generating unit 11 generates the positioninformation after a predetermined period of time after receiving theposition information request signal. In the example illustrated in FIG.5, the position information generating unit 11 generates the positioninformation of the object to be detected on the basis of the digitalsignal output from the A/D converter 15. The position informationincludes the multi-rotation data of the X bits and the absolute positiondata of the Y bits.

The configuration information generating unit 12 generates theconfiguration information (X=m, Y=n) representing the amount of themulti-rotation data (X=m bits), the amount of the absolute position data(Y=n bits), or both. The configuration information preferably includesthe information about the amount of the absolute position data. However,in a case where the amount of data (m+n) is already known, the amount(Y=n) of the absolute position data can be calculated from the amount(X=m) of the multi-rotation data.

The configuration information may include the information indicating theboundary between the absolute position data and the multi-rotation dataduring the serial communication. Specifically, the configurationinformation includes information representing the position of the leastsignificant bit (LSB) of the multi-rotation data or of the absoluteposition data; the position of the most significant bit (MSB) of themulti-rotation data or of the absolute position data; or both theposition of the least significant bit (LSB) and the position of the mostsignificant bit (MSB), the positions being adjacent to the boundarybetween the multi-rotation data and the absolute position data in theposition information.

The control device 20 transmits a first request signal for the positioninformation or the configuration information to the encoder 1 at thestart of the serial communication. Here, the “first request signal” is asignal for requesting the position information or the configurationinformation that the control device 20 transmits to the encoder 1 at thestart of the serial communication. In FIG. 6, for example, the encoder 1receives the first request signal for requesting the positioninformation or the configuration information at the time r1, which isthe start of the serial communication.

When the encoder 1 receives the first request signal from the controldevice 20, the encoder 1 transmits the configuration information alongwith the position information to the control device 20 as a series ofserial data or transmits the configuration information as separateserial data to the control device. In FIG. 6, at the time t1, thetransmission unit 13 transmits the configuration information along withthe position information to the control device 20 as a series of serialdata using serial communication. Alternatively, the configurationinformation may be transmitted as separate serial data to the controldevice.

The storage unit 23 of the control device 20 stores the configurationinformation received from the encoder 1. Accordingly, the configurationof the multi-rotation data and the absolute position data in theposition information received from the second time onward can bedetermined on the basis of the configuration information stored in thestorage unit 23.

The encoder 1 may transmit, to the control device 20, specificationinformation relating to an encoder specification along with theconfiguration information when the encoder 1 receives the first requestsignal from the control device 20. The encoder specification informationpreferably includes at least one of information related to an encoderdrawing number, a model, a serial number, and the like. By transmittingthe encoder specification information, it is possible to check, on thecontrol device side, whether the encoder has been changed.

The control device transmits a second request signal for the positioninformation to the encoder at a predetermined cycle after transmittingthe first request signal. Here, the “second request signal” is a signalfor requesting the position information that is transmitted to theencoder 1 at the predetermined cycle after the control device 20transmits the first request signal to the encoder 1. As illustrated inFIG. 6, at the time r2, the encoder 1 receives the second request signalfor the position information as the request signal transmitted thesecond time.

The encoder 1 transmits the position information as separate serial datato the control device 20 each time (t=t2, t3, . . . ) the encoder 1receives the second request signal from the control device 20. Asillustrated in FIG. 6, at the time t2, the transmission unit 13transmits the position information as Separate serial data to thecontrol device 20. Following that, in a similar manner, each time theencoder 1 receives the second request signal, as a third request signalonward, from the control device 20 after the time t3, the encoder 1transmits the position information as separate serial data to thecontrol device 20.

In this way, in the control system according to Example 2, when theencoder receives the first position information request signal, theconfiguration information is transmitted to the control device onlyonce, and the configuration information received by the control deviceis stored. With such a configuration, the encoder can transmit theconfiguration information only once, can transmit only the positioninformation from the second time onward, and is thus able to provide amargin in the serial data transmitted by the encoder.

In the above description, an example is given in which the encodertransmits the configuration information only once after receiving theposition information request signal, but the present invention is notlimited to such an example. For example, by transmitting theconfiguration information periodically, it is possible to confirm thatthere is no change in the configuration of the position information.Further, when the configuration of the position information of theencoder is changed, the configuration information may be transmittedeach time the position information is changed. An example of a case inwhich the configuration information is changed includes a case in whichthe configuration of the position information is changed in accordancewith the size of the position information; or a case in which theencoder is changed.

Then, a control system according to Example 3 is described. FIG. 7illustrates a configuration diagram of a control system according toExample 3. A control system 103 according to Example 3 is provided withthe encoder 1 and a control device 200 that controls a target object byusing information transmitted by serial communication from the encoder1.

The encoder 1 of the control system 103 according to Example 3 has thesame configuration as the encoder 1 in the control system 101 accordingto Example 1.

The position information generating unit 11 of the encoder 1 generatesthe position information including the absolute position data and themulti-rotation data of the object to be detected. The configurationinformation generating unit 12 of the encoder 1 generates theconfiguration information representing the distribution of the absoluteposition data and the multi-rotation data in the amount of data duringthe serial communication. The transmission unit 13 transmits theposition information corresponding to the configuration information tothe control device 200.

The control device 200 in the control system 103 according to Example 3includes the reception unit 21, the storage unit 23, and a notificationunit 24.

The reception unit 21 receives the position information and theconfiguration information transmitted from the encoder 1. The storageunit 23 stores the configuration information received from the encoder 1by the reception unit 21. The notification unit 24 performs thenotification of a configuration mismatch when the configurationinformation stored in the storage unit 23 does not match theconfiguration information received by the reception unit 21 the nexttime.

Then, in the control system according to Example 3, a procedure isdescribed in which a warning or the like is issued when the controldevice 200 receives configuration information that is different from theconfiguration information stored in the storage unit. First, a case isdescribed in which the configuration information transmitted from theencoder 1 changes to configuration information that is different fromthe configuration information received by the control device 200 in thepast. FIG. 8 illustrates an example in which the configurationinformation transmitted from the encoder changes in the control system101 according to Example 1. In FIG. 8, it is assumed that normalconfiguration information d1 transmitted by the encoder 1 is informationindicating that the multi-rotation data is 12 bits and the absoluteposition data is 16 bits. At this time, the configuration informationmay be abnormal due to noise, a component failure, and the like, or theconfiguration information may change as a result of the encoder beingreplaced. For example, as illustrated in FIG. 8, it is assumed that theconfiguration information d1 has changed, on the serial communicationcircuit, to configuration information d2 indicating that themulti-rotation data is 11 bits and the absolute position data is 17bits.

In the control system according to Example 1, the control device 2 isnot provided with the storage unit and therefore cannot recognizechanges in the configuration information, and the configurationinformation d2 that has changed from the normal configurationinformation is used as it is. As a result, since the weight of theposition data (the distribution of the multi-rotation data and theabsolute position data) changes, the control is executed on the basis ofthe erroneous position information.

In contrast, in the control system 103 according to Example 3, first,the storage unit 23 stores the normal configuration information receivedfrom the encoder 1. FIG. 9A illustrates a state in which the controldevice 200 stores the normal configuration information initiallytransmitted from the encoder in the control system according to Example3. It is assumed that the normal configuration information d1 in theresponse signal transmitted by the encoder 1 is the informationindicating that the multi-rotation data is 12 bits and the absoluteposition data is 16 bits. The storage unit 23 stores this normalconfiguration information d1.

FIG. 9B illustrates an example in which, after the storing of theconfiguration information initially transmitted from the encoder in thecontrol system according to Example 3, the next transmittedconfiguration information has changed. For example, on the serialcommunication circuit, it is assumed that the normal configurationinformation d1 has changed to the configuration information d2indicating that the multi-rotation data is 11 bits and the absoluteposition data is 17 bits. Examples of cases in which the configurationinformation is transmitted multiple times include cases in which theencoder has been changed, the control system has been reactivated, theconfiguration information has been transmitted multiple times to confirmthat the configuration information has not been changed, etc.

The notification unit 24 performs the notification of the configurationmismatch when the normal configuration information (X=12, Y=16) storedin the storage unit 23 does not match the configuration information(X=11, Y=17) received by the reception unit 21 the next time. Thecontrol device 200 may stop controlling the target object (the motor 10,for example) to be controlled by the control device 200 when thenotification unit 24 performs the notification of the configurationmismatch.

In this way, according to the control system according to Example 3, bystoring the configuration information of the encoder 1 (theconfiguration of the position data) in the control device 200, acomparison can be made with the configuration information that has beentransmitted again, and when a change is found, an operation abnormalitycan be prevented by generating warning information; or by stopping theprocessing of the position information in conjunction with generatingthe warning information. In addition, also in a case in which theconfiguration information is misread, the operation abnormality can beprevented by generating the warning information; or by stopping theprocessing of the position information in conjunction with generatingthe warning information. Further, it is possible to check whether theencoder has been replaced using the fact that the configurationinformation has changed.

The control device 200 may further include a display device 25 thatdisplays the configuration mismatch as visual information. In a case inwhich the notification unit 24 generates the warning information orgenerates a command to stop the processing of the position information,the notification unit 24 may display, on the display device 25, thepossibility that the encoder may have been replaced with anotherencoder. By performing such display, a user can easily recognize thepossibility that the encoder may have been replaced.

Further, the transmission unit 13 of the encoder 1 may transmit theencoder specification information together with transmitting theconfiguration information. The encoder specification informationpreferably includes at least one of information related to the encoderdrawing number, the model, the serial number, and the like. Further, thetransmission unit 13 may transmit the encoder specification informationwhen the control device 200 transmits a signal requesting the encoderspecification information. By transmitting the encoder specificationinformation, it is possible to check, on the control device side,whether the encoder has been changed.

The control device 200 may further include an update processing unit 26that overwrites the configuration information stored in the storage unit23 with the configuration information received by the reception unit 21the next time. With such a configuration, the position information canbe processed by using the configuration information of a new encoderafter the encoder has been replaced with the new encoder.

The control unit 22, the notification unit 24, and the update processingunit 26 provided in the control device 200 can be realized by hardware,such as a circuit implementing the functions thereof, or can be realizedby a computing device, such as a CPU, using software implementingfunctions equivalent thereto.

1. A control system comprising: an encoder; and a control deviceconfigured to control a target object by using information transmittedfrom the encoder by serial communication, wherein the encoder includes aposition information generating unit configured to generate positioninformation made of a predetermined amount of data and includingabsolute position data of an object to be detected, a configurationinformation generating unit configured to generate configurationinformation representing a ratio of the absolute position data in theamount of data during serial communication, and a transmission unitconfigured to transmit, to the control device, the position informationand the configuration information as a series of serial data, and thecontrol device includes a reception unit configured to receive theposition information and the configuration information transmitted fromthe encoder and a control unit configured to process the positioninformation received by the reception unit on the basis of theconfiguration information received by the reception unit.
 2. The controlsystem of claim 1, wherein the control device transmits, to the encoder,a request signal for the position information at a predetermined cycle,and each time the encoder receives the request signal from the controldevice, the encoder transmits, to the control device, the positioninformation and the configuration data as the serial data.
 3. Thecontrol system of claim 1, wherein the configuration informationincludes information about an amount of the absolute position data. 4.The control system of claim 1, wherein the position informationgenerating unit generates the position information including theabsolute position data and multi-rotation data of the object to bedetected, and the configuration information generating unit generatesthe configuration information representing a distribution of theabsolute position data and the multi-rotation data in the amount of dataduring the serial communication.
 5. The control system of claim 4,wherein the configuration information includes information about anamount of one of the absolute position data and the multi-rotation data.6. The control system of claim 4, wherein the configuration informationincludes information indicating a boundary between the absolute positiondata and the multi-rotation data during the serial communication.
 7. Anencoder provided in the control system of claim 1, wherein thetransmission unit is configured to transmit, to the control device, theposition information corresponding to the configuration informationtogether with the configuration information.